Tmux – How to Reset Background to Transparent

There is some information on 256-color support in the tmux FAQ.

Detecting the number of colors that the terminal supports is unfortunately not straightforward, for historical reasons. See Checking how many colors my terminal emulator supports for an explanation. This means that

• tmux cannot reliably determine whether the terminal supports more than 8 colors;
• tmux cannot reliably communicate to the application that it supports more than 8 colors.

When you're in tmux, the terminal you're interacting with is tmux. It doesn't support all of xterm's control sequences. In particular, it doesn't support the OSC 4 ; … control sequence to query or set color values. You need to use that while directly running in xterm, outside tmux.

If you run tmux -2, then tmux starts with 256-color support, even if it doesn't think that your terminal supports 256 colors (which is pretty common).

By default, tmux advertises itself as screen without 256-color support. You can change the value of TERM in .tmux.conf to indicate 256-color support:

set -g default-terminal "screen-256color"

You can use TERM=xterm-256color or TERM=screen-256color on Ubuntu. These values will only cause trouble if you log in to a remote machine that doesn't have a termcap/terminfo entry for these names. You can copy the entries to your home directory on the remote machine; this works with most modern terminfo implementations.

# From the Ubuntu machine to a machine that doesn't have *-256color terminfo entries
ssh somewhere.example.com mkdir -p .terminfo/s .terminfo/x
scp -p /lib/terminfo/s/screen-256color somewhere.example.com:.terminfo/s/
scp -p /lib/terminfo/x/xterm-256color somewhere.example.com:.terminfo/x/

From your screenshot it looks like you are running into an issue with your terminal being toe narrow for everything powerline throws into the default tmux config. I ran into something similar recently¹. It seems powerline does not degrade its tmux config for narrow terminals as gracefully as its vim one. There are, however, at least two things you can adjust:

1. Copy the powerline module configurations to your home directory if you haven't already and modify the theme for tmux. Try dropping some of the modules until what remains will fit on your line.

2. Change the overall length allotted to the status segments. As these are set in the powerline.conf file you are including, you will need to set them in your .tmux.conf after that include:

   set -g status-left-length 20
   set -g status-right-length 150
   

   Those are the default values. Try reducing them until something fits.

Note due to the width settings as noted above, if I narrow the terminal below a few more columns, the right status segment will disappear altogether leaving just the left and window pane name segments:

Edit: I just noticed that your tmux version is 1.8. I don't know for sure if that will effect you but I do know there were major changes to the way status bars are configured going into 1.9 and a quick look through the powerline source shows they are doing version checking for < 1.9 and using a degraded feature set for earlier versions. It looks like you should still get a right status of some sort, but that might be complicating your debug process. I highly recommend upgrading to the latest tmux.

_{¹ I just recently implemented powerline across my zsh, vim, tmux, and awesome configs, spent a week with it, and yesterday abandoned it. It was just too much pain for too little gain, especially with having to work across multiple distros and OSes. I have, however, implemented basically the same thing without the bulk. My tmux config for example is basically a rip-off of the output of powerline in plain tmux values that are ealies to get working on different hosts. For vim I went with airline; for my zsh prompt I wrote my own theme for prezto that uses powerline-ish features.}